A hydraulic excavator including a position detecting unit configured to detect the current position of a work point of working equipment has been known. For instance, in a hydraulic excavator disclosed in Patent Literature 1, the position coordinates of a blade edge of a bucket is calculated based on position information from a GPS antenna. Specifically, the position coordinates of the blade edge of the bucket are calculated based on parameters such as a positional relationship between the GPS antenna and a boom pin, the respective lengths of the boom, arm and bucket, and the respective direction angles of the boom, arm and bucket. The position coordinate of each of the arm and bucket is calculated based on a sensor output value acquired from, for instance, a stroke sensor, which is attached to a cylinder for swinging each of the arm and bucket to acquire an extension/retraction state of the cylinder.
With such a technique, the position of the blade edge of the bucket can be estimated by a controller of the hydraulic excavator to move the blade edge of the bucket in conformity with a designed excavated surface, thereby preventing the excavated surface from being excessively excavated with the bucket and efficiently performing the excavation work.
For the above technique, it is important that the controller of the hydraulic excavator should accurately detect the position of the blade edge of the bucket. Accordingly, in the technique disclosed in Patent Literature 1, for instance, five of the attitudes of the blade edge of the bucket of the working equipment are measured by an external measurement device such as a total station, and the controller of the hydraulic excavator calibrates working equipment parameters necessary for calculation of the position of the blade edge based on the resulting measurement value of the blade edge of the bucket.